Date: 2015aug17
OS: Windows8Keywords: OSX
Q. How do I stop those Windows 10 nag messages?
A. There is a program called GWX.exe that runs all the time (!)
that produces these messages.
Using Task Manager (you can get it with Ctrl-Alt-Del) stop it.
Then so it doesn't start again, rename its folder:

cd c:\windows\system32
rename GWX GWX.HIDE

You may need to take ownership.
And there is a registry key so a futue update won't replace it: